How to crop an MR in Display

Start display with your volume to crop as input:
Display volume_to_crop.mnc

Then press on:
H - Volume cropping
F - Set Crop Source (Enter file name in terminal window)
S - Pick Crop Box

A green contour will appear around the MR planes. You can move the side of this crop window with your mouse.
Click on S again to move another side of the cropping box.

To save this new cropped volume:
R - Crop to file (Enter file name in terminal window)